The present invention relates to an ink tank, a cartridge including the ink tank, and a printing apparatus using the cartridge, and more particularly, an ink tank supplying ink to a printhead which performs printing according to an ink-jet printing method, a cartridge including the ink tank, and a printing apparatus employing the cartridge.
Conventionally, as a method of detecting the amount of ink residue in an ink tank containing ink or detecting existence/absence of ink in the ink tank, optical detection of the amount of ink residue or ink existence/absence is known.
For instance, Japanese Patent Application Laid-Open (KOKAI) No. 8-112907 discloses an ink-jet printing apparatus which detects the amount of ink residue in an ink tank having a negative pressure generating material e.g. absorbent material, foaming material or the like, by transmitting light through a part of the transparent wall surface of the ink tank and detecting changes in optical reflectance in the boundary portion between the wall surface of the ink tank and the negative pressure generating material.
Furthermore, Japanese Patent Application Laid-Open (KOKAI) No. 7-218321 discloses an ink tank comprising an optical ink detection unit which is formed with a light-transmitting material made of the same material as the ink tank, and the boundary surface between ink and the optical ink detection unit has a predetermined angle with respect to an optical path. Still further, Japanese Patent Application Laid-Open (KOKAI) No. 9-29989 discloses an ink-jet printing apparatus capable of detecting existence/absence of ink and existence/absence of an ink tank by a single photosensor serving as both light-emission device and photoreceptor.
Besides the aforementioned apparatuses, Japanese Patent Application Laid-Open (KOKAI) No. 7-89090 discloses an apparatus for detecting existence or absence of liquid in a liquid container comprising: a negative-pressure-generating-material housing chamber which houses a negative pressure generating material and has a liquid supply opening and an air hole; and a liquid containing chamber which has a channel connected with the negative-pressure-generating-material housing chamber and forms a substantially enclosed space.
Herein, the conventional ink existence/absence detection mechanism utilizing a light-transmitting prism is explained with reference to FIG. 6. FIG. 6 shows a positional relation among a light-transmitting prism provided on the bottom surface of an ink tank, a light emission device which emits light on the prism, and a photoreceptor which receives the emitted light.
As shown in FIG. 6, a prism 1060 is integrally molded to the bottom portion 1061 of the ink tank. Light emitted externally by a light emission device 1062 from the bottom of the ink tank is incident on the prism 1060.
When the ink tank is sufficiently filled with ink, the incident light takes the optical path Ixe2x86x92IIxe2x80x2 as shown in FIG. 6 and is absorbed by the ink, so that the light does not return to the photoreceptor 1063. On the other hand, when the ink is consumed and the ink tank contains no ink, the incident light is reflected by the oblique portion of the prism 1060 and takes the optical path Ixe2x86x92IIxe2x86x92III, then reaches the photoreceptor 1063 as shown in FIG. 6. In the foregoing manner, ink existence/absence is detected by whether or not the light emitted by the light emission device 1062 returns to the photoreceptor 1063.
Note that the light emission device 1062 and photoreceptor 1063 are provided in the main body of a printing apparatus.
The above-described ink existence/absence detection mechanism may be regarded as a rational method of realizing detection of an ink level or ink existence/absence in an ink tank at low cost.
Meanwhile, another configuration is also known for performing such optical ink residue detection. More specifically, water repellent processing is performed on a component provided in the optical path so as to avoid an ink droplet from being attached to the component. By this configuration, even when the amount of ink in the ink tank decreases, it is possible to avoid erroneous ink residue detection caused by the ink droplet attached to the surface of the component provided in the optical path.
For instance, Japanese Patent Application Laid-Open (KOKAI) No. 7-237300 discloses a construction utilizing silicone or Teflon resin as a water repellent agent in order to avoid ink droplet attachment to the side wall surface of the ink tank or light reflector, serving as a component provided in the optical path. In addition, Japanese Patent Application Laid-Open (KOKAI) No. 8-187873 discloses a technique of performing surface processing such as water repellent or oil repellent processing on the inner wall surface of an ink tank, which serves as a component provided in the optical path, instead of polishing the inner wall surface of the ink tank to reduce the surface roughness thereby enlarging the contact angle between ink and the ink tank inner wall surface.
However, recently, higher image quality and higher printing quality are required in ink-jet printing apparatuses, and the types of ink used in printing apparatuses are diversified. Inks used are, for instance, an aqueous pigment ink in which pigment serving as a colorant is dispersed in water with the use of a dispersant, or an aqueous pigment ink utilizing self-dispersing pigment capable of stable dispersion without using a dispersant by reforming the surface of the pigment, or a dispersing-type ink such as micro-emulsion ink or the like in which an oil-base dye is dispersed by emulsification.
Inventors of the present invention have used such ink, in which a colorant is dispersed, in the above- described conventional examples, and discovered that in the environment of a high temperature, even if there is no ink droplet attached to the inner portion of an ink tank, light emitted by a light emission device for ink residue detection and incident upon the ink tank does not always return to a photoreceptor.
As a result of careful study of the above problem by the inventors, the inventors have discovered that, particularly in the environment of a high temperature, dispersion of the colorant becomes unstable and the colorant adsorbs to the inner wall of the ink tank. When the colorant adsorbs to the inner wall of the ink tank, the light emitted by the light emission device for ink residue detection and incident upon the ink tank is absorbed by the colorant adsorbed to the inner wall of the ink tank.
Because of this, despite the fact that ink does not exist in the ink tank, determination is made that ink still exists in the ink tank.
The present invention is made in consideration of the result of the above study, and has an object to provide an ink tank which enables accurate detection of existence/absence of liquid even when using the type of ink in which a colorant is dispersed, a cartridge including the ink tank, and a printing apparatus employing the cartridge.
According to one aspect of the present invention, the foregoing object is attained by providing an ink tank, in which a part of a storage containing ink where a colorant is dispersed, is coated with a low surface energy processing agent including alkyl polysiloxane.
Herein, it is preferable that acid be included in the low surface energy processing agent.
Furthermore, it is preferable that the alkyl polysiloxane coated on the part of the storage be 1 to 15 xcexcg per unit area (1 mm2).
Furthermore, the storage comprises a prism having a first surface which receives light emitted by an external device, and a second surface which receives the light reflected by the first surface and changes an optical path of the light received such that the optical path of the light is headed to the external device, the prism formed with a light-transmitting material, provided on a bottom portion of the storage, and protruded from the bottom portion of the storage toward an interior of the storage, wherein the prism is coated with the low surface energy processing agent.
Still further, only the first surface and the second surface of the prism may be coated with the low surface energy processing agent.
According to another aspect of the present invention, the foregoing object is attained by providing an ink tank, in which a part of a light-transmitting wall surface which forms a storage containing ink where a colorant is dispersed, has lower surface energy than other portions of the wall surface.
Furthermore, it is preferable that a low surface energy processing agent including alkyl polysiloxane be coated on the part of the light-transmitting wall surface having low surface energy.
Furthermore, it is preferable that the ink tank comprises a prism having a shape of substantially polygonal prism where the part of the light-transmitting wall surface constitutes a plurality of reflection surfaces having a predetermined angle with respect to an optical path of light emitted from a light source located externally at a predetermined position, wherein a side surface of the prism is coated with the low surface energy processing agent including alkyl polysiloxane.
According to still another aspect of the present invention, the foregoing object is attained by providing an ink tank comprising: a storage containing ink where a colorant is dispersed; and a residual amount detector for optically detecting ink residue contained in the storage, wherein the residual amount detector is provided on a part of a wall surface which forms the storage, and the residual amount detector is coated with a low surface energy processing agent including alkyl polysiloxane and acid so as to have lower surface energy than other portions of the wall surface where the residual amount detector is not provided.
Herein, it is preferable that the storage comprises: a first chamber containing the ink only and forming a substantially enclosed space; a second chamber containing an absorbent which retains ink by absorbing ink and serves as a negative pressure generating material; and a channel where the first and second chambers are connected, wherein the first chamber includes the residual amount detector, and the second chamber includes an outlet for externally discharging liquid and an opening for introducing outside air.
According to still another aspect of the present invention, the foregoing object is attained by providing an ink tank, in which a part of a storage containing solution in which solvent includes insoluble or slightly soluble fine particles, is coated with a low surface energy processing agent including alkyl polysiloxane.
According to the aforementioned ink tank, since the surface of a part of the storage containing liquid in the ink tank is coated with a low surface energy processing agent, it is possible to create a surface energy difference in the inner wall of the liquid storage. By virtue of this, even in the case of utilizing an aqueous pigment ink in which pigment serving as a colorant is dispersed in water with the use of a dispersant, or an aqueous pigment ink utilizing self-dispersing pigment capable of stable dispersion without using a dispersant by reforming the surface of the pigment, or a dispersing-type ink such as micro-emulsion ink or the like in which an oil-base dye is dispersed by emulsification, attachment (adhesion) of the colorant to the surface-processed portion (having low surface energy) is suppressed, and the colorant is attached preferentially to other portions (having high surface energy) whose surface is not processed. As a result, it is possible to prevent attachment of the colorant to the surface processed portion (having low surface energy).
Accordingly, assuming that the surface processed portion is a prism provided in the optical path of optical ink residue detection, even when using the type of ink where a colorant is dispersed, existence or absence of liquid (ink) can be accurately detected.
According to still another aspect of the present invention, the foregoing object is attained by providing a cartridge including the ink tank having aforementioned configuration, the cartridge comprising: a printhead for discharging liquid contained in the ink tank; and a holder for holding the ink tank.
Herein, it is preferable that the ink tank be detachable from the holder.
Furthermore, it is preferable that the printhead be an ink-jet printhead which performs printing by discharging ink. In this case, the ink-jet printhead includes heat energy transducers for generating heat energy to be applied to the ink so that the printhead discharges ink by utilizing the heat energy.
According to still another aspect of the present invention, the foregoing object is attained by providing a printing apparatus for printing an image on a print medium by using the ink tank having aforementioned configuration, the printing apparatus comprising: a printhead for performing printing by discharging ink contained in the ink tank; optical means for emitting light to the residual amount detector and receiving reflection light from the residual amount detector; detection means for detecting a residual amount of liquid contained in the ink tank based on the optical means; and control means for controlling printing operation performed by the printhead based on the detection result obtained by the detection means.
Note that in the specification of the present invention, xe2x80x9cweightxe2x80x9d or xe2x80x9c%xe2x80x9d indicates a percentage by weight unless specified otherwise.
Moreover, the prism according to the present invention is formed with a light-transmitting material, and comprises a surface which constructs a part of an external wall surface of a liquid container such as an ink tank, and a plurality of reflection surfaces which are different from the aforementioned surface, and whose boundary surface with contents (e.g., ink) of the storage has a predetermined angle with respect to the optical path. The prism is structured such that the amount of light reflected by the reflection surfaces differs depending on existence or absence of the contents of the liquid storage. Therefore, the plurality of reflection surfaces are protruded toward the interior of the container. Note that instead of the plurality of reflection surfaces, a curved surface may be provided.
The present invention is particularly advantageous because, by coating the low surface energy processing agent not on the entire inner wall surface of the ink tank, but on the prism provided in an optical path of optical ink residue detection, it is possible to create a lower surface energy portion compared to other portions of the inner wall surface of the ink tank, which are in contact with ink. Therefore, even under a severe ink storage condition, a part of the composition of the liquid, e.g., colorant or the like, does not attach to remain on the prism surface. Accordingly, the prism is always kept in an excellent state for reflecting light, and therefore liquid existence/absence can be accurately detected.
Furthermore, by virtue of including acid in the low surface energy processing agent having alkyl polysiloxane, it is possible to increase the adsorbent of the alkyl polysiloxane which has adsorbed to the inner wall surface of the liquid container such as an ink tank.
Other features and advantages of the present invention will be apparent from the following description taken in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the figures thereof.